A switched-mode power supply (SMPS), also referred to simply as a switcher, is an electronic power supply that incorporates a switching regulator in order to be highly efficient in the conversion of electrical power. Like other types of power supplies, an SMPS transfers power from a source like the electrical power grid to a load while converting voltage and current characteristics. An SMPS is usually employed to efficiently provide a regulated output voltage, typically at a level different from the input voltage. Unlike a linear power supply, the pass transistor of a switching mode supply switches very quickly (typically between 50 kHz and 1 MHz) between full-on and full-off states, which minimizes wasted energy. Voltage regulation is provided by varying the ratio of on to off time. In contrast, a linear power supply must dissipate the excess voltage to regulate the output. This higher efficiency is the chief advantage of a switched-mode power supply.
Switching regulators may be used as replacements for linear regulators when higher efficiency, smaller size or lighter weight is required. However, they are more complicated, their switching currents can cause electrical noise problems if not carefully suppressed, and simple designs may have a poor power factor.
A SMPS may be used to provide power for personal computers, various types of mobile devices such as cellular telephones and personal digital assistants (PDA), games and toys, home entertainment systems, office and industrial applications, etc.